PolymerMom: "Each boy gains access to 1/3 of the trust assets at 25, another 1/3 of the assets at 30 and the rest of the assets at 35. MDH, as trustee, will override those provisions as he sees fit - probably long before they turn 30.)"

Those are unually percentages. It is typically 1/3 at x age (often 25), 1/2 of the remaining balance at y age (often 30) because 1/2 of 2/3 is 1/3, and the rest at z age (often 35).